PROJECT SUMMARY In North America, 75,000 patients per year require a shunt for issues with intracranial pressure annually, with total annual costs over $1 billion in the US. The surgery to implant a shunt is usually effective in treating hydrocephalus and it is the most common brain surgery in children. However, 50% of the shunts placed will fail within 2 years, requiring surgical replacement. Children presenting with hydrocephalus symptoms, such as headache and confusion, undergo indirect evaluation of the shunt performance to determine if shunt malfunction is likely. This evaluation is followed by surgery if shunt malfunction is suspected. There is no non-invasive technique to directly measure the CSF flow through an implanted shunt. The purpose of this proposal is to develop a non-invasive, quantitative measure of CSF shunt flow using magnetic resonance imaging (MRI). Leveraging a previous method developed to image very slow blood flow movement in the capillaries and arterioles in the brain, the current project team will adapt it to measure the slow flow of CSF in a shunt. The team combines expertise in MRI sequence development, neurosurgery, and radiology to provide a clinical tool, called Shunt-FENSI, to enable accurate, quantitative and robust measurement of flow in an implanted shunt. The Shunt-FENSI tool will be optimized and evaluated with a CSF shunt phantom, in patients with extraventricular drainage, in healthy children with an implanted shunt, and in children with suspected shunt failure. In addition to developing and validating the Shunt-FENSI tool, normative ranges of flow and ranges of flow for which symptoms appear will be characterized in a sample population of children with shunts.